It is known that 2,2-dimethyl-3-halogenated vinyl-cyclopropanecarboxylic acid ester of benzyl alcohol substituted with 1 to 4 fluorine atoms and 0 to 2 chlorine atoms, has excellent insecticidal activity. In particular, DE-A-3705224 discloses that a cyclopropanecarboxylic acid ester of 2,3,5,6-tetrafluorobenzyl alcohol has a high insecticidal ability and that it is less toxic to mammals than a cyclopropanecarboxylic acid ester of pentafluorobenzyl alcohol and is therefore a superior insecticide.
WO 9808795 proposes a process for producing fluorinated benzyl alcohol, in which process fluorinated dicyanobenzene is hydrogenolyzed in the presence of a catalyst to hydrodecyanate only one cyano group to produce fluorinated benzonitrile and the cyano group of the fluorinated benzonitrile is converted to a hydroxymethyl group. This process is useful for the purpose of producing 2,3,5,6-tetrafluorobenzyl alcohol at high purity and in high yields.
However, the above production of fluorinated benzonitrile by hydrogenolysis of fluorinated dicyanobenzene involves so large amounts of catalyst that the cost of production is significantly affected.